The administration of fluids to a patient is typically accomplished by inserting a catheter into a patient's vein, and then coupling a source of fluid thereto using an administration set including flexible tubing and one or more couplings or fittings. Occasionally, medication is prescribed by a physician and administered by injecting a dosage of the medication from a syringe into the catheter. This can be accomplished by temporarily disconnecting the catheter from the source of fluid and then coupling the syringe to the catheter.
Alternatively, Y-connectors are customarily incorporated in the administration set to merge fluids from two or more sources to a common tube and to the patient. A typical Y-connector has a self-sealable inlet at one branch, known as an injection site, through which the tip of a piercing member can penetrate for injecting medication. The source of fluid is coupled to a second branch of the Y-connector and remains connected while administering the medication via the first branch. These injection sites usually include an elastomeric plug, sometimes referred to as a "septum" to form a liquid seal.
To avoid accidental sticking while administrating a dosage to the Y-connector, a drug transfer spike, comprised of a cannula is typically attached to the syringe in place of a conventional hypodermic needle. The drug transfer spike has a blunt tip which is adapted to pierce and penetrate the sealable inlet or septum at the injection site. By implementing pre-slit septums in combination with drug transfer spikes having blunt tips, accidental punctures which might other wise result from the use of a standard syringe having a sharp-tipped hypodermic needle are avoided.
In U.S. Pat. No. 5,199,948 to McPhee, a needleless valve is disclosed having a pre-slit septum. The septum is held in place in a housing inlet by a cap affixed thereabout. The septum disclosed has a concave upper surface which bulges and flattens when disposed in the housing inlet and retained by the cap. A drug transfer spike is disclosed having a ball-shaped tip, pointed enough to penetrate the diaphragm of a drug vial, but which is not sharp enough to puncture human skin. The McPhee injection set comprises a total of three pieces. It does not include a locking mechanism for restricting accidental withdrawal of the drug transfer spike from the septum of the injection site.
U.S. Pat. No. 5,167,648 to Jepson et al. also teaches a pre-slit injection site and an associated cannula. A resealable septum is disposed in a cylindrical housing having tapering interior walls and the outer surface of the septum is forced into a dome-like shape due to axial forces applied to the septum's perimeter by the housing's swaged end members. The septum disclosed includes an elastomeric disc with a zero-clearance slit defined axially therethrough.